Well drilling tool

ABSTRACT

There are disclosed several embodiments of a well tool which is adapted to be connected as part of a pipe string through which drilling fluid is circulated, and which comprises inner and outer members which are rotated with respect to one another by a motor between them.

This application is a continuation-in-part of my copending applications,Ser. No. 584,964, filed June 9, 1975, and entitled "Well Drilling Tool,".Iadd.now abandoned .Iaddend.and Ser. No. 546,006, filed Jan. 31, 1975,and entitled "Well Drilling Tool" and now U.S. Pat. No. 3,971,450.

This invention relates to improvements in a well tool of the type whichis adapted to be connected as part of a pipe string through whichdrilling fluid is circulated, and which comprises inner and outermembers which are supported for relative rotation and sealed withrespect to one another by means of bearings and seals, respectively,within an annular space between them in which a motor for causing theirrelative rotation is contained.

In one such type of tool which is used in the drilling of a well, theinner member comprises a shaft connected to a drill bit, and the outermember comprises a tubular member connected to the lower end of a drillstring, whereby the bit may be rotated by means of the motor withoutrotation of the drill string. In a so-called turbodrill, the motor is ofa fluid type, comprising turbine blades on the inner and outer memberswhich are driven by the circulation of drilling fluid through theannular space between them. Upon passage through the turbine section,the drilling fluid is confined for passage out through the bit on thelower end of the shaft.

In another drilling tool of this general type, such as that disclosed inU.S. Pat. No. 3,656,565, the shaft member is connected at its oppositeends to the drill string and bit, and the tubular member is caused torotate with respect to the shaft member by means of the motortherebetween, whereby spiral blades carried about the tubular member areuseful in reducing bottom hole pressure in the well bore. As in the caseof a turbodrill, the motor may comprise turbine blades on the shaft andtubular members within the annular space between them, and the drillingfluid which is circulated through the motor is confined for passage outthrough the bit.

Due to the drop in pressure across the turbine section and the bit,there is a substantial pressure differential across the seal means ofdrilling tools of this type; and, as well known, a rotary seal meanswhich divides pressure in this manner is subject to considerably greaterwear than one which merely divides fluids at the same pressure. Thisproblem of wear is even more serious due to abrasive particles in thedrilling fluid which find their way between the surfaces of the sealmeans and the tubular members which they engage.

Unless protected therefrom, the bearings mounted in the annular spaceare also damaged by the abrasive particles in the drilling fluid. Sincetheir replacement requires raising and lowering the drill string atgreat expense, efforts have been made to exclude drilling fluid from thebearings by containing them in a lubricant chamber formed at least inpart by a pair of seal means in the annular space. However, if one orboth of these seal means also functions as a pressure divider, itbecomes worn and eventually permits the well fluid abrasives to enterthe lubricant chamber.

U.S. Pat. No. 3,659,662, discloses a tool which is intended to overcomethis problem by providing a tool in which a labyrinth is provided withinthe annular space, and the tubular member is ported in such a mannerthat the pressure drop is taken across the labyrinth, and pressure isequalized across the seal means forming the lubricant chamber in whichthe bearings are contained. However, if the passages through thelabyrinth are small, they tend to be clogged by the particles in thedrilling fluid, thereby lessening the cooling effect; and, if they areso large as to pass a large volume of drilling fluid, the drillingefficiency of the bit is lowered considerably. Furthermore, even if thelabyrinth is to be replaced by a third seal means of the non-leakingtype, as disclosed in my aforementioned copending application, Ser. No.546,006, it might still be subject to damage by the tendency ofparticles in the drilling fluid to enter between the sealing faces.

The primary object of this invention is to provide a tool of this typein which the pressure dividing seal means is protected from the damagingeffect of the drilling fluid particles.

Another object is to provide such a tool in which the bearing means isalso protected in such a manner that it need not be contained in aseparate lubricant chamber, thereby eliminating the necessity ofadditional seal means for defining the chamber.

These and other objects are accomplished in accordance with theillustrated embodiments of this invention, by a tool of the typedescribed including seal means between the members for separating fluidon the outer side of the tool from that within the annular space abovethe seal means, and a body of material within the space above the sealmeans which includes a metallic weighting substance which is liquidduring drilling operations, and which has a specific gravity which issufficiently greater than that of the drilling fluid and which issufficiently insoluble with the drilling fluid, during drillingoperations, that it substantially excludes drilling fluid therefrom.Consequently, the seal means is protected despite the presence ofabrasives in the drilling fluid which would otherwise damage the sealmeans, and thereby permit it to leak. Ordinarily, the material is alubricant which, in addition to excluding mud from the seal means,facilitates operation of the tool by reducing the frictional resistanceto relative rotation between the shaft member and tubular member.

In the preferred embodiment of the invention, the bearing means whichsupports the members for relative rotation is contained within theannular space above the seal means but beneath the upper level of thelubricant. In this manner, the lubricant not only facilitates operationof the bearing means, but also protects it as well as the pressuredividing seal means, so that it is unnecessary to provide additionalseal means within the annular space to define a separate lubricantchamber for the bearing means.

In alternative embodiments of the invention, the bearing means isinstead contained within a variable volume lubricant chamber which isdefined at least in part between an additional pair of seal means; and,as in the above-described tool, the additional seal means separate thelubricant therein from fluid at substantially the same pressure--in oneform that on the inside of the tool, and, in another form, that on theoutside of the tool. Consequently, there is substantially no pressuredifferential across the additional seal means so that the lubricant maybe a conventional type having a specific gravity substantially less thanthat of the drilling fluid. Although requiring additional means, andthus usually less preferred than the first embodiment of the tool, theselatter embodiments may be preferred in the event the drilling fluidrequires the use of a seal protecting lubricant which is so heavy as tointerfere with operation of the bearing means.

Drilling fluids are usually water base "muds" consisting of water, clayand barite, and having sufficiently high density to contain highformation pressures which might be encountered in drilling a well.During circulation within the well, the drilling mud also picks up"drill solids" such as sand and shale, which add to the abrasiveness ofthe barite particles. Such muds have densities greater than conventionallubricants, and some have specific gravities of about 2.4 to 2.5.

Since mud having the above-noted density is presently the heaviestnormally used during drilling operations, and further since formationpressures requiring such a heavy mud are not always encountered, thisinvention contemplates that a seal protecting lubricant having aspecific gravity of not substantially less than 2.5 may be heavy enough.On the other hand, large differentials between the specific gravities ofthe mud and lubricant make it more difficult for the two materials to bemixed with another, so that a lubricant having a higher specific gravitymay be desired. In fact, in the event the tool is to be left in the wellbore over an extended period of time, during which abrasive particles inthe mud might otherwise settle out above the upper level of thelubricant, a specific gravity such as 4.5 or at least higher than thatof the barite (4.2) is preferred.

There are instances, however, in which a well is drilled with a lighterdrilling fluid, such as when the formation pressure is quite low, andcare must be taken to prevent losing circulation of the drilling fluid.However, such drilling fluids are of an oil-base type which isinherently soluble with conventional lubricants. Hence, the inventioncontemplates that while the seal protecting lubricant for such use neednot be much heavier than conventional lubricants, it must besufficiently insoluble with the drilling fluid to substantially excludedrilling mud from the seal means, and the bearing means, whereappropriate, during drilling operations.

Since agitation is known to promote the mixture of two otherwiserelatively insoluble materials, the tool of this invention also includesa ring which fits relatively closely within the annular space and floatson the interface between the drilling mud and the seal protectinglubricant. In addition to minimizing agitation, the ring tends to keepthe lubricant from running out of the annular space in which it iscontained, as when the tool is laid down on its side during non-use.

The specific gravity of conventional grease type lubricants may beincreased by the addition of solid metal particles thereto. Siliconebase greases are preferred due to their stability insofar as temperatureis concerned as well as their greater resistance to mixing with drillingmud. Alternatively, lead, copper, zinc, silver and the like, or alloysthereof with other materials, which are known to be good lubricants, maybe used as the seal protecting lubricant. Although in solid form atambient surface level temperatures, such materials may be liquid underconditions encountered in the bearing means during drilling operations.In fact, downhole temperatures are often so high that they reduce theviscosity of the lubricants.

The use of a metal or a metal impregnated liquid as a seal protectinglubricant has the added advantage of acting as a heat conductor, and assuch, it serves to dissipate much of the heat generated in the bearingmeans during drilling operations.

The selection of lubricant materials which are sufficiently insolublewith the drilling fluid is well within the realm of one having ordinaryskill in the art, having in mind that in a broad sense, the term"soluble" is used not only to include chemical solutions, but alsodispersions and other mixtures of the drilling fluid and lubricant whichwould permit substantial amounts of the drilling fluid to penetrate thelubricant. In this respect, it will also be appreciated that smallintrusions of solid particles from the drilling fluid may not damage theseal means or the bearing means, where appropriate, to such an extent asto interfere with the intended use of the tool during a reasonable timeframe. In this regard, it is contemplated that the bearing means shouldnot become unduly damaged between trips of the drill string in and outof the well bore, and preferably not during the expected lifetime of adiamond bit, which is presently about 200 hours of drilling.

The seal protecting lubricant may be made from a silicone greasemanufactured by the Dow Corning Corporation of Midland, Michigan, andknown as "Dow Corning Valve Seal," to which are added particles of abismuth-lead-tin-cadmium alloy manufactured by the Cerro SalesCorporation, of New York, New York, and known as "Cerrobend." Althoughthe exact chemical composition of this particular grease is not known tome, it is merely one of many suitable greases which may be used, havingin mind the objects of the present invention and the well knowncharacteristics of similar grease, which are readily available topersons skilled in the art in publications such as Chemistry andTechnology of Silicones, by Walter Noll, published in 1968 (see pages455-474). Although the exact chemical composition of this particularalloy is also not known to me, other alloys having substantially thesame characteristics are known to consist of about 50% bismuth, 26.7%lead, 13.3% tin, and 10.0% cadmium, by weight. Although having aspecific gravity of just slightly above 1.0, this grease, when mixedwith a sufficient volume of alloy, preferably ground into fineparticles, will result in a lubricant having a specific gravity in theorder of 4.5.

Although solid at ambient surface level temperatures, an alloy of thistype has a low melting point and thus will be liquid when used in thetool in the well bore. Furthermore, this melting point is below thedisintegration temperature of the silicone grease.

Obviously, other conventional lubricants may be used as a base inproducing the desired seal protecting lubricant. Also, of course, otherheavy metals, such as silver, lead or Mercury may be found suitable,although the above-described alloy is preferred due to its mixability ata relatively low temperature. Still further, it may also be desired tomix lubricant additives, such as graphite or molybdenom disulfide, tothe mixture.

In the drawings, wherein like reference characters are used throughoutto designate like parts:

FIG. 1 is a vertical sectional view of the first described type of toolconstructed in accordance with the preferred embodiment of the presentinvention;

FIG. 2 is a vertical sectional view of such a tool constructed inaccordance with a first alternative embodiment of the invention; and

FIG. 3 is a vertical sectional view of such a tool constructed inaccordance with a second alternative embodiment of the invention.

With reference now to the details of the above described drawings, tool10 constructed in accordance with the first embodiment of the inventionis shown in FIG. 1 to comprise an outer tubular member 11 suspended fromthe lower end of a drill string 12 disposed within a well bore B, and aninner shaft member 13 supported for rotation within the outer member andhaving a bit 14 on its lower end which rests on the bottom of the wellbore. More particularly, the tool 10 is a turbodrill having means to bedescribed for causing the shaft member and thus the bit 14 to rotatewith respect to the drill string in response to circulation of drillingfluid downwardly through the drill string, out the bit and upwardlywithin annulus A between the well bore and the tool.

Outer tubular member 11 is mounted concentrically about the inner shaftmember 13 to provide an annular space 15 between them which is open atits upper end to the outside of the tool. A turbine section T isdisposed within an upper portion of the space, and a bearing 16 isdisposed within the space below the turbine section T for rotatablysupporting the shaft member from the tubular member. More particularly,a seal means 17 is disposed within the space 15 below the turbinesection and bearing 16 for sealing between the members, and thusconfining drilling fluid for circulation downwardly through the turbinesection T and out the bit 14. Seal means 17 contains the pressuredifferential between the inside and outside of the tool which resultsfrom the pressure drop in drilling fluid as its passes through the bit.

Seal means 17 comprises Chevron type packing disposed between inner andouter sleeves 18 and 19 fitting closely about the outer diameter ofshaft member 13 and closely within inner diameter of tubular member 11,respectively. The inner sleeve 18 is supported on an upwardly facingshoulder 20 about shaft member 13, and the outer sleeve 19 is supportedon a nut 21 at the lower end of tubular member 11. The inner and outerraces bearing means 16 are supported on the upper ends of the inner andouter sleeves and are held down by means of annular shoulders 22 and 22Aon the shaft and tubular members, respectively.

The turbine section T of the tool 10 comprises turbine blades 23 on theupper end of the shaft member arranged in alternative relation withrespect to turbine blades 24 on upper end of tubular member 11. Shaftmember 13 is closed at 25 to divert drilling mud circulating downwardlythrough the drill string 12 into the upper end of annular space 15 forpassage through the turbine section. As shown, the upper end of shaft 13is open to form a chamber 26 having a port 27 connecting its upper endwith the inside of tubular member 11.

Upon passage through the turbine section T, drilling mud passes throughports 30 in the shaft member beneath solid section 25 into a bore 28through the lower end of the shaft member for circulation downwardlyinto the aligned bore 29 of the drill bit 14. The drilling mud isdiverted into the ports 30 by means of a diverter flange 33 which fitsclosely within the outer member 11 and has an inner diameter forming arestricted passage about shaft member 13. Although the restrictedpassage permits mud to pass into space 15 above the bearings, itminimizes turbulence therein and also filters out shale and other largeparticles in the mud.

The turbine blades 23 and 24 may be constructed with their upper facesangled in opposite directions so that the flow of drilling mudtherethrough rotates the shaft member with respect to the tubularmember, in a manner well known in the art. Preferably, and as shown, theturbine blades are carried on sleeves which are stacked one above theother about the shaft member and within the tubular member. The turbinesection is shown as discontinuous since, as will be appreciated, it willordinarily be of considerable length.

In accordance with the novel aspects of the present invention, theportion of the annular space 15 above seal means 17 is filled with aheavy lubricant 31 having the previously described characteristics withrespect to the drilling mud. More particularly, and as shown in FIG. 1,the lubricant is filled to an upper level well above the bearing 16, butbelow the ports 30. Although there may be some loss of lubricant pastthe seal means 17, there is obviously an excess of same within theannular space for protecting the bearings and the seal means from thedrilling mud. Also, although the lower end of the seal means 17 isexposed to the drilling mud, such mud is at a lower pressure than thatwithin the tool, so that the abrasive particles in the drilling mud donot get between the sealing surfaces of the seal means and the inner andouter members of the tool.

As previously described, a ring 32 is relatively closely received withinthe annular space between the outer diameter of shaft member 13 and asleeve 34 on the inner diameter of outer member 11 for floating on theinterface between the drilling mud and lubricant 31. For this purpose,the ring 32 is made of a material which has a higher specific gravitythan mud, but a lower specific gravity than the lubricant. As alsopreviously described, the primary function of the ring 32 is to reduceagitation at the interface between the drilling mud and lubricant whichmight otherwise promote their mixture. Furthermore, of course, since thering 32 fits relatively closely within the annular space, and since thelubricant is a heavy material, ring 32 further serves to contain thelubricant within the annular space when the tool is laid down on itsside.

Sleeve 34 is seated on an upwardly facing shoulder 35 on outer member11, and supports diverter flange 33, which in turn supports turbineblades 24. The turbine blades 23 are supported on a shoulder 38 aboutshaft member 13, and are held down by a cap 39 on the upper end of theshaft member through which port 27 is formed.

Annular space 15 above bearings 16 may be filled with liquid lubricantthrough suitable port (not shown) in tubular member 11 and sleeve 34,below ring 32. During filling, the ring 32 forms a limit stop byengagement with the lower end of diverter ring 33. If a solid (atsurface temperature) lubricant is used, it may first be heated to permitit to be poured into the space, and then permitted to solidify in thespace as it cools.

Tool 100 constructed in accordance with one form of the secondembodiment of the invention is shown in FIG. 2 to be similar in manyrespects to tool 10 of FIG. 1. Thus, it also comprises an outer tubularmember 101 suspended from the lower end of a drill string 102 disposedwithin a well bore B, and an inner shaft member 103 supported forrotation within the outer member and having a bit 104 at its lower endwhich rests on the bottom of the well bore. Furthermore, as in the caseof the tool 10, tool 100 is a turbodrill having means for causing theshaft member and thus the bit 14 to rotate with respect to the drillstring in response to circulation of drilling fluid downwardly throughthe drill string, out the bit, and upwardly within the annulus A betweenwell bore and the tool.

As was also true of tool 10, outer tubular member 11 is mountedconcentrically about the inner shaft member 13 to provide an annularspace 105 between them which is open at its upper end to the inside ofthe tool and at its lower end to the outside of the tool, a turbinesection T is disposed within an upper portion of the space, and abearing 106 is disposed within the space below the turbine section forrotatably supporting the shaft member from the tubular member. Stillfurther, a seal means 107 is disposed within the space 105 below theturbine section T for sealing between the members to confine drillingfluid for circulation downwardly through the turbine section and out thebit. Although, as compared with the tool 10, seal means 107 is mountedwithin the annular space above bearing 106, a port P₁ is formed in outermember 101 to fluidly connect a portion of chamber 105 intermediate theseal means and the bearing with the exterior of the tool, whereby sealmeans 107 functions similarly to seal means 17 in that it contains thepressure differential between the inside and outside of the tool.

As shown in FIG. 2, seal means 107 comprises Chevron type packingbetween inner and outer sleeves 109A and 109 fitting closely about theouter diameter of shaft 103 and closely within the inner diameter oftubular member 101, respectively. The inner sleeve 109A is supported ona ring 109B, which in turn is supported on a sleeve 108 above the innerrace of bearing 106, and the outer sleeve 109 and lower end of thepacking of seal means 107 are supported on a flange 110, which in turnis supported on the upper end of an outer sleeve 111 above the outerrace of bearing 106. The inner race of bearing 106 is supported on asleeve 112 which in turn is supported on an upwardly facing shoulder 113about a lower portion of shaft member 103, and the outer race of thebearing is supported on an outer sleeve 114, which in turn is supportedby means of a nut 115 on the lower end of outer tubular member 101.Sleeve 111 is of course ported in alignment with port P₁ through outertubular member 101.

The turbine section T of tool 100 is shown to be identical to that oftool 10 in that it comprises turbine blades 116 on the upper end of theshaft member arranged in alternative relation with respect to turbineblades 117 on the upper end of tubular member 101. Also, as in the caseof shaft member 13 of tool 10, the upper end of shaft member 103 is opento form a chamber 118 connected by means of a port 119 at its upper endwith the inside of outer tubular member 101. Shaft member 103 also hasports 120 therein beneath chamber 118 to permit drilling mud to passfrom the turbine section into bore 121 through the lower end of theshaft, and thus into the bore 122 of bit 104. Still further, there is aflange 123 on the inner diameter of the tubular member beneath theturbine section for diverting the mud into the ports 120, and thus forpassage downwardly to bit 104, the lower end of the flange beingsupported on the upper end of sleeve 109, and the turbine blades 117being stacked above the flange.

Bearing 106 is disposed within lubricant 126 contained within alubricant chamber C₁ within a lower portion of annular space 105 whichis defined at its upper end by seal means 124 and at its lower end byseal means 125. As shown, each such seal means is vertically slidablewithin the annular space so as to vary the volume of the chamber C₁ inresponse to changes in fluid pressure above and below the seal means. Inthis latter respect, because of the port P₁ in this outer tubular memberabove upper seal means 124, both seal means are subject to substantiallythe same fluid pressure--namely, that of drilling fluid in the annulusA.

Since the seal means 124 and 125 are free to compensate for changes inthis pressure, there is substantially no pressure differential acrossthem, and thus little tendency for the lubricant to leak from thechamber. Consequently in this embodiment of the invention, the bearingmeans may be protected by disposal within a conventional lubricant, eventhough of substantially less specific gravity than that of the drillingmud.

On the other hand, a portion of the annular space 105 above the pressuredividing seal means 107 is filled with a heavy lubricant 127 havingcharacteristics with respect to the drilling fluid which were previouslydescribed in connection with lubricant 31 of tool 10. In this respectthen, lubricant 127 protects the seal means 107 in the same sense thatlubricant 31 in the tool 10 protects seal means 17. However, since thebearing means 106 is protected within the pressure compensating chamberC₁, the level of lubricant 127 need only be sufficiently high to protectseal means 107, having in mind a sufficient reserve to compensate forthe small leakage of lubricant which might take place past the sealmeans 107, as well as the need for maintaining the level of thelubricant 127 below the ports 120. As in the case of tool 10, since thedrilling fluid to which the lower end of the seal means 107 is exposedis at a lower pressure than that within the tool, the abrasive particlestherein do not get between the sealing surfaces of seal means 107 andthe inner and outer members of the tool.

A ring 128 fits relatively closely between the inner and outer sleeves109A and 109 within the annular space 105 above bearing 106 for floatingon the interface between the drilling mud and lubricant 127. Thus, as inthe case of ring 32 of tool 10, ring 128 is made of a material which islighter than the lubricant, but heavier than the drilling mud, so thatit will remain at the interface.

Tool 200 constructed in accordance with another form of the secondembodiment of the invention is shown in FIG. 3 to be identical, in manyrespects, to tool 100 of FIG. 1. Thus, many parts of the tool 200 bearthe same reference characters as corresponding parts of tool 100, exceptfor the prefix "2" instead of "1," and where the functions of theseparts are the same as those of corresponding parts of tool 100, theirdescription will not be repeated.

The primary differences between the tools 100 and 200 are that, in thelatter, bearing 206 which rotatably supports shaft member 203 connectedto bit 204 from tubular member 201 connected to drill string 202 isdisposed above, rather than below, a pressure dividing seal means 207,and the portion of an annular space 205 between the members which isintermediate the bearing and a variable volume pressure chamber C₂within which the bearing and seal means are disposed is fluidlyconnected by means of a port P₂ in a shaft member 203 to the inside,rather than to the outside, of the tool. As a consequence, although thepressure differential between the inside and outside of the tool iscontained by seal means 207, as in the case of the tool 100, the fluidpressure above and below seal means 224 and 225 defining the upper andlower ends of lubricant chamber C₂ are subject to the fluid pressure onthe inside, rather than on the outside, of the tool. In any event,however, since seal means are subjected to substantially the samepressure, and further since the seal rings 224 and 225 are verticallyslidable within the annular space 205, there is essentially no pressuredifferential across them. Thus, similarly to the chamber C₁ of tool 100,bearing chamber C₂ may be filled with a conventional lubricant 226having a specific gravity substantially lower than that of the drillingmud.

On the other hand, although disposed beneath bearing 206, seal means 207nevertheless contains the pressure differential between drilling fluidwithin the tool (which has access to the annular space above seal means207 through ports P₂) and that on the exterior of the tool. Similarly totool 100, lubricant 227 in a portion of the annular space above sealmeans 207 is of the heavier variety having the characteristics withrespect to the drilling fluid identical to those previously described inconnection with lubricant of tool 100. Thus, as in the case of tool 100,lubricant 227 protects seal means 207 by being maintained at a levelthereabove sufficient to compensate for any small leakage past the sealmeans 207, and bearing 206 is otherwise protected from the drillingfluid inasmuch as it is disposed within the pressure compensatingchamber C₂.Still further, and again as in the case of the tool 100,abrasive particles in the drilling fluid do not get between the sealingsurface of seal means 207 and the inner and outer members of the toolinasmuch as such fluid beneath the seal means is at a lower pressurethan that within the tool.

As in tool 100, turbine blades 216 and 217 are mounted on the shaftmember and tubular member, respectively, within the upper end of space205. Also, drilling fluid passing through the turbine section isdiverted into ports 220 by means of flange 223, and thus into bore 221in the shaft member leading to bore 222 in the bit.

The Chevron type packing making up seal means 207 is disposed between anouter sleeve 209 fitting closely within the inner diameter of the outertubular member 201, and an inner sleeve 208 which fits closely about theouter diameter of shaft member 203. The lower end of the inner sleeve208 is supported on a shoulder 213 about the shaft member, and the lowerend of outer sleeve 209 is supported by a nut 215 threaded to the lowerend of outer member 201. Outer sleeve 209 extends upwardly to support aring 230, which in turn supports an outer sleeve 209A extending upwardlyto support outer race of bearing 206. Inner sleeve 208 extends upwardlyto support the inner bearing race, and is ported intermediate its lengthin alignment with port P₂ in the shaft member.

The lower seal means 225 defining the lower end of chamber C₂ issealably slidable within outer sleeve 209A and the upper end of innersleeve 208. The upper seal means 224 defining the upper end of chamberC₂ is sealably slidable within an inner sleeve 210 which is supportedabove the inner bearing race and fits closely about the outer diameterof the shaft member, and outer sleeve 211 which is supported above theouter bearing race and fits closely within the inner diameter of thetubular member. The outer sleeve 211 supports a flange 223 which divertsthe flow of drilling fluid into ports 220, and the turbine blades 217mounted on the outer member are stacked above the flange 223 inalternating relation with turbine blades 216. The upper end of innersleeve 210 is held down by a nut 231 threaded about shaft 203 beneathports 220.

From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forth,together with other advantages which are obvious and which are inherentto the apparatus.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:
 1. A well tooladapted to be connected as part of a pipe string through which drillingfluid is circulated, comprising inner and outer members defining anannular space therebetween having one end opening to the inside of thetool and another end opening to the outside of the tool, bearing meanson the members within said space supporting them for rotation withrespect to one another, motor means within said space for so rotatingthe members, means sealing between said members .[.for separating thefluid on the other side of said tool from that.]. within the said space.[.above the seal means.]., and a body of material within the spaceabove the sealing means which .[.includes a metallic weighting substancewhich is liquid during drilling operations, said material having.]..Iadd.(a) comprises a liquid whose specific gravity is not substantiallygreater than that of the drilling fluid, but which is impregnated withmetal particles whose specific gravity is substantially greater thanthat of the drilling fluid so that said material has .Iaddend.a specificgravity which is sufficiently greater than that of the drilling fluidand .[.being.]. .Iadd.(b) which is .Iaddend.sufficiently insoluble withthe drilling fluid, during drilling operations, that it substantiallyexcludes drilling fluid .[.therefrom.]. .Iadd.from the sealingmeans.Iaddend..
 2. A tool of the character defined in claim 1, whereinthe material has a specific gravity of not substantially less than 2.5.3. A tool of the character defined in claim 2, wherein the.[.material.]. .Iadd.liquid .Iaddend.is a lubricant.
 4. A tool of thecharacter defined in claim 2, wherein the material has a specificgravity of not less than 4.5.
 5. A tool of the character defined inclaim 4, wherein the .[.material.]. .Iadd.liquid .Iaddend.is alubricant. .[.6. A tool of the character defined in claim 1, wherein themetallic weighting substance comprises metal particles of high densitymaterial..].
 7. A tool of the character defined in claim .[.6.]..Iadd.1.Iaddend., wherein the .[.material also includes.]. .Iadd.liquidis .Iaddend.a grease type lubricant.
 8. A tool of the character definedin claim .[.6.]. .Iadd.1.Iaddend., wherein said .[.material alsoincludes.]. .Iadd.liquid is .Iaddend.a silicone type lubricant.
 9. Atool of the character defined in claim 1, wherein the .[.material is.].metal .[.which is.]. .Iadd.particles are .Iaddend.solid at ambientsurface level temperatures .Iadd.and liquid during drillingoperations.Iaddend..
 10. A tool of the character defined in claim 9,wherein the .[.material.]. .Iadd.liquid .Iaddend.is a lubricant.
 11. Atool of the character defined in claim 1, including a ring which fitsrelatively closely in said annular space and floats on the interfacebetween said drilling fluid and material.
 12. A tool of the characterdefined in claim 1, wherein the motor means comprises turbine blades onthe inner and outer members above the level of the material.
 13. A toolof the character defined in claim 1, wherein the upper end of the outermember has means thereon for connection to the lower end of the drillstring, and the lower end of the inner member has means thereon forconnection to the bit.
 14. A tool of the character defined in claim 1,wherein the bearing means is above the sealing means.
 15. A tool of thecharacter defined in claim 1, wherein the bearing means is below thesealing means.
 16. A well drilling tool adapted to be connected to thelower end of a drill string above the drill bit, whereby drilling fluidmay be circulated downwardly through the inside of the tool and upwardlywithin the annulus between the outside of the tool and the bore of thewell being drilled, comprising inner and outer members defining anannular space therebetween having one end opening to the inside of thetool and another end opening to the outside of the tool, bearing meanson the members within said space supporting them for rotation withrespect to one another, motor means within said space for so rotatingthe members, means sealing between said members beneath the bearingmeans .[.for separating the fluid on the outer side of said tool fromthat.]. within the said space .[.above the seal means.]., and a body ofmaterial within the space above the sealing means which .[.includes ametallic weighting substance which is liquid during drilling operationsand which.]. has an upper level above the bearing means so that thebearing means is contained therein, .[.said material having.]. .Iadd.and(a) comprises a liquid whose specific gravity is not substantiallygreater than that of the drilling fluid, but which is impregnated withmetal particles whose specific gravity is substantially greater thanthat of the drilling fluid so that said material has .Iaddend.a specificgravity which is sufficiently greater than that of the drilling fluidand .[.being.]. .Iadd.(b) which is .Iaddend.sufficiently insoluble withthe drilling fluid, during drilling operations, that it substantiallyexcludes drilling fluid .[.therefrom.]. .Iadd.from the sealing andbearing means..Iaddend.
 17. A tool of the character defined in claim 16,wherein the material has a specific gravity of not substantially lessthan 2.5.
 18. A tool of the character defined in claim 17, wherein the.[.material.]. .Iadd.liquid .Iaddend.is a lubricant.
 9. A tool of thecharacter defined in claim 17, wherein the material has a specificgravity of not substantially less than 4.5.
 20. A tool of the characterdefined in claim 19, wherein the .[.material.]. .Iadd.liquid .Iaddend.isa lubricant. .[.21. A tool of the character defined in claim 16, whereinthe metallic weighting substance comprises metal particles of highdensity material..].
 22. A tool of the character defined in claim.[.21.]. .Iadd.16.Iaddend., wherein the .[.material also includes.]..Iadd.liquid is .Iaddend.a grease type lubricant.
 23. A tool of thecharacter defined in claim .[.21.]. .Iadd.16.Iaddend., wherein said.[.material also includes.]. .Iadd.liquid is .Iaddend.a silicone typelubricant.
 24. A tool of the character defined in claim 16, wherein the.[.material is.]. metal .[.which is.]. .Iadd.particles are.Iaddend.solid at ambient surface level temperatures .Iadd.and liquidduring drilling operations.Iaddend..
 25. A tool of the character definedin claim 24, wherein the .[.material.]. .Iadd.liquid .Iaddend.is alubricant.
 26. A tool of the character defined in claim 16, including aring which fits relatively closely in said annular space and floats onthe interface between said drilling fluid and material.
 27. A tool ofthe character defined in claim 16, wherein the motor means comprisesturbine blades on the inner and outer members above the upper level ofsaid material.
 28. A tool of the character defined in claim 27, whereinthe turbine blades are above the bearing means, and there is at leastone port in the inner member connecting the annular space with theinterior of the inner member intermediate the lowermost turbine bladesand the upper level of said material.
 29. A tool of the characterdefined in claim 16, wherein the upper end of the outer member has meansthereon for connection to the lower end of the drill string, and thelower end of the inner member has means thereon for connection to thebit.
 30. A well drilling tool adapted to be connected to the lower endof a drill string above the drill bit, whereby drilling fluid may becirculated downwardly through the inside of the tool and upwardly withinthe annulus between the outside of the tool and the bore of the wellbeing drilled, comprising inner and outer members defining an annularspace therebetween, bearing means on the members within said spacesupporting them for rotation with respect to one another, motor meanswithin said space for so rotating the members, first means sealingbetween said members for separating the fluid on one side of said toolfrom that within a portion of said space, means providing a variablevolume lubricant chamber including second and third sealing meansbetween said members above and below said bearing means within the spaceportion and means fluidly connecting the other side of the tool withsaid space portion above and below said second and third sealing means,respectively, whereby said first seal means is adapted to contain thepressure differential between the inner and outer sides of the tool, andsaid second and third sealing means separate the chamber between themfrom the fluid on said other side of the tool, a body of material withinthe space above the first sealing means which includes a metallicweighting substance .[.which is liquid during drilling operations andwhich has an upper level above the bearing means so that the bearingmeans is contained therein.]., said material having a specific gravitywhich is sufficiently greater than that of the drilling fluid and beingsufficiently insoluble with the drilling fluid, during drillingoperations, that it substantially excludes drilling fluid.[.therefrom.]. .Iadd.from the sealing means.Iaddend..
 31. A welldrilling tool of the character defined in claim 30, wherein said firstsealing means is below the second and third sealing means to separatethe fluid on the outer side of the tool from said space portion, and thefluidly connecting means connects the space portion above and below thesecond and third sealing means with the inner side of the tool.
 32. Awell drilling tool of the character defined in claim 30, wherein saidfirst sealing means is above the second and third sealing means toseparate the fluid on the inner side of the tool from said spaceportion, and the fluidly connecting means connects the space portionabove and below the second and third sealing means with the outer sideof the tool.
 33. A well drilling tool of the character defined in claim30, wherein one member comprises a shaft member having means forconnection to the bit, and the other member has means for connecting itto the lower end of the drill string.
 34. A well drilling tool of thecharacter defined in claim 33, wherein said one member is the innermember, and said other member is the outer member.
 35. A well drillingtool of the character defined in claim 30, wherein at least one of saidsecond and third sealing means comprises a seal ring which is verticallyslidable within said space portion to permit the volume of said chamberto vary.
 36. A tool of the character defined in claim 30, wherein thematerial has a specific gravity of not substantially less than 2.5. 37.A tool of the character defined in claim 36, wherein the material is alubricant .Iadd.impregnated with metal particles.Iaddend..
 38. A tool ofthe character defined in claim 36, wherein the material has a specificgravity of not substantially less than 4.5.
 39. A tool of the characterdefined in claim 38, wherein the material is a lubricant.Iadd.impregnated with metal particles.Iaddend.. .[.40. A tool of thecharacter defined in claim 30, wherein the metallic weighting substancecomprises metal particles of high density material..].
 41. A tool of thecharacter defined in claim .[.40.]. .Iadd.30.Iaddend., wherein saidmaterial .[.also contains.]. .Iadd.is .Iaddend.a silicone lubricant.Iadd.impregnated with metal particles.Iaddend..
 42. A tool of thecharacter defined in claim 30, including a ring which fits relativelyclosely in said annular space and floats on the interface between saiddrilling fluid and material.
 43. A tool of the character defined inclaim 30, wherein the motor means comprises turbine blades on the innerand outer members above the upper level of said lubricant.
 44. A welltool adapted to be connected as part of a pipe string through whichdrilling fluid is circulated, comprising inner and outer membersdefining an annular space therebetween having one end opening to theinside of the tool and another end opening to the outside of the tool,means on the members supporting them for relative movement with respectto one another, means within said space for so moving the members, meanssealing between said members .[.for separating the fluid on the outerside of said tool from that.]. within the said space .[.above the sealmeans.]., and a body of material within the space above the sealingmeans which .[.includes a metallic weighting substance which is liquidduring drilling operations said material having.]. .Iadd.(a) comprises aliquid whose specific gravity is not substantially greater than that ofthe drilling fluid, but which is impregnated with metal particles whosespecific gravity is substantially greater than that of the drillingfluid so that said material has .Iaddend.a specific gravity which issufficiently insoluble with the drilling fluid and .[.being.]. .Iadd.(b)which is .Iaddend.sufficiently insoluble with the drilling fluid, duringdrilling operations, that .[.is.]. .Iadd.it .Iaddend.substantiallyexcludes drilling fluid .[.therefrom.]. .Iadd.from the sealingmeans.Iaddend..
 45. A tool of the character defined in claim 44, whereinthe material has a specific gravity of not substantially less than 2.5.46. A tool of the character defined in claim 45, wherein the.[.material.]. .Iadd.liquid .Iaddend.is a lubricant.
 47. A tool of thecharacter defined in claim 45, wherein the material has a specificgravity of not substantially less than 4.5.
 48. A tool of the characterdefined in claim 47, wherein the .[.material.]. .Iadd.liquid .Iaddend.isa lubricant. .[.49. A tool of the character defined in claim 44, whereinthe metallic weighting substance comprises metal particles of highdensity material..].
 50. A tool of the character defined in claim.[.49.]. .Iadd.44.Iaddend., wherein the .[.material also includes.]..Iadd.liquid is .Iaddend.a grease type lubricant.
 51. A tool of thecharacter defined in claim .[.49.]. .Iadd.44.Iaddend., wherein said.[.material also includes.]. .Iadd.liquid is .Iaddend.a silicone typelubricant.
 52. A tool of the character defined in claim 44, wherein the.[.material is.]. metal .[.which is.]. .Iadd.particles are.Iaddend.solid at ambient surface level temperatures .Iadd.and liquid.Iaddend.during drilling operations.
 53. A tool of the character definedin claim 52, wherein the .[.material.]. .Iadd.liquid .Iaddend.is alubricant.
 54. A tool of the character defined in claim 44, including aring which fits relatively closely in said annular space and floats onthe interface between said drilling fluid and material.